AU599301B1

AU599301B1 - Polysilane preceramic polymers

Info

Publication number: AU599301B1
Application number: AU83081/87A
Authority: AU
Inventors: Duane Ray Bujalski; Gary Edward Legrow; Thomas Fay-Oy Lim
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 1986-12-22
Filing date: 1987-12-15
Publication date: 1990-07-19
Anticipated expiration: 2007-12-15
Also published as: CA1318442C; GB2234753A; GB8729537D0; DE3743373A1; US4962176A; GB2234753B; FR2643908B1; FR2643908A1; DE3743373C2

Description

COMMONWEALTH OF AUSTRAL 53 1 PATENTr ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class A,*,plication Number: Lodged: .Cq~m.Dlete Specification Lodged: Accepted: Published: Pri~rlty: Retated Art: This &vuLum~t c h Scctioii 49 irnd is corrL.L for printting.I Nal'me of Applicant: Address oi'Applicant i Actual InventorS Address for Service DOW CORNING CORPORATION MIDLAND, STATE OF MICHIGAN, UNITED STATES OF AMERICA DUANE RAY FXIJALSKI, GARY EDWAR1D LEGROW and THOMAS FA4Y-OY LIM EDWD, WATERS SONS? 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification for the invention crititled: POLYSILANE PRECERAMIC POLYMERS The following statement Is a full description of tttis Invention, including the best method of performing It known to us lt 4 -1 a- POLYSILANE PRECERAMIC POLYMERS The United States Government has rights in this invention pursuant to Contract Number F33615-83-C-5006 awarded by the United States Air Force.

ei This invention relates to polysilanes which are useful as preceramic polymers in the preparation of ceramic materials and articles. This invention further relates to the methods of preparing such polysilanes as well as the S ceramics prepared from such preceramic polymers.

i Baney et al. in U.S. Patent 4,310,651 (issued January 12, 1982) disclosed a polysilane of general formula (CHSi)((CH 3 where there was present 0 to 60 mole percent 2 Si) units and 40 to 100 mole percent (CH,Si) units and where the remaining bonds on silicon were attached to other silicon atoms and chlorine atoms or bromine atoms.

The polysilane was converted to a beta-silicon carbide S containing ceramic material at elevated temperatures (about 14000C). The polysilanes of U.S. Patent 4,310,651 generally Sare difficult to handle due to their high reactivity in air.

23 Baney et al. in U.S. Patent 4,298,559 (issued November 3, 1981) prepa\red polysilanes of general formula

(CH

3 where there was present 0 to 60 mole Spercent ((CH 3 2 Si) units and 40 to 100 mole percent (CHSi) units and where the remaining bonds on silicon were attached to other silicon atoms and additional alkyl radicals of 1 to 4 carbon atoms or phenyl radicals. Upon heating these polysilanes were converted into silicon carbide containing ceramics in high yields.

Baney et al. in U.S. Reissue Patent Re. 31,447 (reissued November 22, 1983) disclosed polysilanes of the -2general formula (CHSi)((CH3)2Si) where there was present 0 to 60 mole percent ((CH) 2 ,Si) units and 40 to 100 mole percent (CH 3 Si) units and where the remaining bonds on silicon were attached to other silicon atoms and alkoxy radicals containing 1 to 4 carbon atoms or phenoxy radicals.

Silicon carbide-containing ceramics were obtained by firing these polysilanes to elevated temperatures.

Baney et al. in U.S. Patent 4,314,956 (issued February 9, 1982) disclosed polysilanes of the general formula (CH 3 Si)((CH3) 2 Si) where there was p .zent 0 to mole percent 2 Si) units and 40 to 100 mole percent

(CH

3 Si) units and where the remaining bonds on silicon were attached to silicon and amine radicals of the general formula where R" is a hydrogen atom, an alkyl radical of 1 to 4 carbon atoms or a phenyl radical. A silicon carbidecontaining ceramic was obtained by firing this polysilane to an elevated temperature under an inert atmosphere or under an ammonia atmosphere.

These polysilanes are further discussed in Baney et al. Organometallics, 2, 859 (1983).

Haluska in U.S. Patent 4,546,163 (issued October 8, 1985), prepared polysilanes of the average formula (RSi)(RzSi)(R"d(CHZ=CH)Si) where there was present from 0 to mole percent (R 2 Si) units, 30 to 99.5 mole percent (RSi) units, 0.5 to 15 mole percent (R d(CH:=CH)Si) units, where the remaining bonds on silcon are attached to other silicon atoms and chlorine atoms or bromine atoms, where R is an alkyl radical containing from 1 to 4 carbon atoms, where R'' is an alkyl radical containing 1 to 4 carbon atoms, a vinyl radical, or a phenyl radical, and where d is 1 or 2.

Polysilanes of the same average formula but containing additional alkyl, aryl, alkoxy, aryloxy, substituted amine, or unsubstituted amine radicals attached to silicon were also prepared. These polysilanes could be pyrolyzed at elevated temperatures in an inert atmosphere to produce silicon carbide-containing ceramics. The vinyl-containing polysilanes could be cured, and thus rendered infusible, prior to pyrolysis by exposure to ultraviolet light.

West in U.S. Patent 4,260,78c .ssued April 7, 1981) prepared a polysilane of general rmula

((CH

3 2 Si)(CH 3 (CsHs)Si) by the sodium metal reduction of Sdimethyldichlorosilane and me-hylphenylsilane. The resulting methylphenylpolysilanes had very high softening points So.' (greater than 280 0

C).

04 tt West et al. in Polym. Prepr., 25, 4 (1984) discloseI the preparation of a polysilane of general formula

(CH,(CH,=CHCH

2 )Si)(CH(CC6H )Si) by the sodium metal reduction of allylmethyldichlorosilane and methylphenyldichlorosilane, These polysilanes were rapidly gelled by irradiation with ultraviolet light.

What has been newly discovered are polysilanes of the general formula (R 2 Si)(RSi)(R'Si) where there are also bonded to the silicon atoms other silicon atoms and chlorine or bromine atoms, where R is an alkyl radical containing 1 to 4 carbon atoms, and where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula Ay X (y)Si(CH 2 wherein eac:h A is independently selected from a hydrogen atom or alkl radicals containing 1 to 4 carbon atoms, y is an inzeger equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1.

These polysilane preceramic polymers can be pyrolyzed at elevated temperatures under an inert atmosphere to yield ceramic materials or articles. These polysilanes may sFso be converted into other preceramic polymers which can be pyrolyzed to ceramic materials or articles. These kz _i ii

#I

*4 4 4 4 04 48 4r 44 o 400 polysilanes represent a significant advance in the art of preparing ceramic materials or articles, especially in the art of preparing ceramic fibers.

This invention relates to polysilanes, which are solid at 25 0 C, having the average formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl radicals containing 1 to 4 carbon atoms, where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A yX(3 Si(CH 2 wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where there are from 0 to 40 mole percent (R 2 Si) units, 1 to 99 mole percent (RSi), and 1 to 99 mole percent (R'Si) units and wherein the remaining bonds on silicon are attached to either other silicon atoms, chlorine atoms, or bromine atoms.

This invention further relates to a method of preparing a polysilane of average formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl radicals containing 1 to 4 carbon atoms, where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula AX 2-Y Si(CH wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, where there are from 0 to 40 mole percent (R 2 Si) units, 1 to 99 mole percent (RSi), and 1 to 99 mole percent (R'Si) units, and wherein the remaining bonds on silicon are attached to e± her other silicon atoms4 chlorine atoms, or bromine atoms, where such method consists of treating a mixture containing a chlorine-containing or bromine-containing disilane and 1 to weight percent of a monoorganosilane of formula R'SiX 3 where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A X _Si(CH, 2 wherein each A is y z independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than S or equal to 1. with 0.001 to 10 weight percent of a rearrangement catalyst at a temperature of 100°C to 340 0

C

o while distilling by-pro-luced volatile materials until there :s00 is produced a polysilane, which is a solid at 25 0 C, having o o the average formula (R 2 Si)(RSi)(R'Si) where R is an alkyl radical containing 1 to 4 carbon atoms, where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula o A X Si(CH 2 wherein each A is independently selected o y 3 z from a hydrogen atom or alkyl radicals containing 1 to 4 o 0H carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, 0 and where there are f:rom 0 to 40 mole percent (RS' units, 1 o'o to 99 mole percent (RSi), and 1 to 99 mole percent (R'Si) *a units and wherein the remaining bonds on silicon are attached 0 to either other silicon atoms, chlorine atoms, or bromine atoms.

The polysilanes of this invention are described by the average unit formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl groups containing 1 to 4 carbon atoms, where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A X YSi(CH2) wherein each A is a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to -6- 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where there are from 0 to 40 mole percent

(R

2 Si) units, 1 to 99 mole percent (CH 3 Si) units, and 1 to 99 mole percent (R'Si) units wherein the remaining bonds on silicon are attached to either other silicon atoms, chlorine atoms, or bromine atoms. These are chlorine- or bromi containing polysilanes where the remaining bonds on silico'.

are attached to other silicon atoms and chlorine atoms or bromine atoms. Preferably, these chlorine- or bromine- 9* containing polysilanes contain from 0 to 40 mole perceit %o (R 2 Si) units, 40 to 99 mole percent (CH 3 Si) units, and 1 to mole percent (R'Si) units. It is most preferred that 0o these chlorine- or bromine-containing polysilanes contain 0 o o to 10 mole percent (R 2 Si) units, 80 to 99 mole percent (RSi) units, and 1 to 20 mole percent (R'Si) units. The chlorine- S, containing polysilanes are preferred in the practice of this invention.

It Especially preferred polysilanes are described by the average formula 2 Si)(CH 3 Si)(R'Si) where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A X wSi(CH,) wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1 and wherv. there are from 0 to 40 mole percent

((CH

3 2 Si) units, 1 to 99 mole percent (CH3Si) units, and 1 to 99 mole percent (R'Si) units wherein the remaining bonds on silicon are attached to either another silicon atom or a chlorine atom. Preferably, these chlorine- or brominecontaining methylpolysilanes contain from 0 to 40 mole percent (R 2 Si) units, 40 to 99 mole percent (CH 3 Si) units, and 1 to 30 mole percent (R'Si) units. It is most preferred 1 that these chlorine- or bromine-containing methylpolysilanes contain 0 to 10 mole percent ((CH3 3 2 Si) units, 80 to 99 mole percent (CH 3 Si) units, and 1 to 20 mole percent (R'Si) units.

The newly discovered polysilanes may be prepared by reacting a mixture of about 40-99 weight percent of one or more chlorine-containing or bromine-containing disilanes and 1 to 60 weight percent of one or more monoorganosilanes of formula R'SiX 3 where R' is selected from the group consisting S of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A IX _y)Si(CH 2 S* wherein each A is independently selected from a hydrogen atom Sor alkyl radicals containing 1 to 4 carbon atoms, y is an S integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, with 0.001 to weight percent of a rearrangement catalyst at a temperature of 100 0 C to 340 0 C while distilling by-produced volatile materials. Preferably, the newly discovered polysilanes are prepared by reacting a mixture of about 70-99 weight percent of one or more chlorine-containing or bromine-contaiining disiianes and 1 to 30 weight percent of one or more monoorganosilanes of formula R'SiX where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phen-l radicals, and radicals of the formula A X _Si(CH 2 z wherein each A is independently selected y 3

Z

from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, with 0.001 to 10 weight percent of a rearrangement catalyst at a temperature of 100 0 C to 3400C while distilling by-produced volatile materials.

The chlorine-containing or bromine-containing disilanes used to prepare the polysilanes are of the general formula (RbXcSi)2 wherein R is an alkyl radical containing I -I -8from 1 to 4 carbon atoms, b has a value of 0 to 2.5, c has a value of 0.5 to 3, the sum equals three, and X is chlorine or bromine. R in the above disila-& may be phenyl, methyl, ethyl, propyl or butyl. Examples of such disilanes include CH 3 C1 2 SiSiC1(CH 3 2 CHCl 2 SiSiCl 2

CH

3

CH

3 Br 2 SiSiBr(CH 3 2

CH

3 Br 2 SiSiBr 2

CH

3 and the like.

Preferably in the above disilane, R is a methyl radical and X is chlorine. The disilane can be prepared from the appropriate silanes or the disilane can be utilized as it is found as a component of the process residue from the direct synthesis of organochlorosilanes. The direct synthesis of organochlorosilanes involves passing the vapor of an organic oo chloride over heated silicon and a catalyst, See Eaborn, "Organosilicon Compounds," Butterworths Scientific 0 Publications, 1960, page 1. The disilanes CH 3

CI

2 SiSiCl 2

CH

3 and (CH,),ClSiSiCl 2

CH

3 are founa in large quantities in the residue from the reaction and, therefore, this Direct Process residue is a good starting material for obtaining the polysilane polymer used in this invention.

OF1. The monoorganosilanes used to prepare the polysilanes of this invention are of formula R'SiX, where R' 'is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula AyX Si(CIH 2 wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1. The A radicals in the formula A yX(3y)Si(CMH) may be the same or different. Generally, the monoorganosilane should have a boiling point of about 180 0 C or greater at one atmosphere. Such a high boiling point reduces the possibility of 4 the monoorganosilane being remove from the reaction mixture before it can be incorporated in-to the -9polysilane. Examples of suitable monoorganosilanes include phenyltrichlorosilane, n-hexyltrichlorosilane, n-octyltrichlorosilane, phenyltribromosilane, n-octyltribromosilane, ClSiCHCH 2 SiC1l, CH 3 C1,SiCH 2

CH

2 SiC1, 2C1SijCH,CH 2 SiC1 3

H(CH

3 2 SiCHCH 2 SiCS,. and the like. Phenyltrichlorosilane and n-octyltrichlorosilane are the preferred monoorganosilanes.

Mixtures of such nonoorganosilanes may also be used, Indeed, mixtures of monoorganosilanes are generally preferred in the practice of this invention. One especially Spreferred mixture of rmonoorganosilanes contains n-octyl.trichlorosilane and phenyltrichlorosilane. The use of such o monoorganosilanes, either singly or in mixtures, appears to Sallow for control of both the softening or glass transition Stemperatures of the polysilanes and other preceramic polymers 0 prepared from the polysilanes and the relative silicon and carbon content of the ceramic materials produced from the polysilane8 and other preceramic polymers prepared from the 4, S polysilrries. The preceramic polymers prepared from the polila nes of this invention are described in detail in tml, Au l308%8 -a V\ 3080 97 entitled "Alkylpoly(polysilyla, e r-Pi'ramic Polymers" and "Derivatized A ane Preceramic Polymers" which were Thi s control is achieved by a variation of the (RP'Sij content in the polysilanes of this invention. In general, it appears that increasing the (R'Si) content of the preceramic polymers results in a reduction in the glass trns-,ition temperature.

Incorporation of (n-octyl-Si) units allows for a significant reducti4n of the glass transition temperature with the amount of the reduction being dependent on the level of (n-octyl-Si) units in the preceramic polymer, Incorporation of (phenyl-Si) units a\so results in a decrease in the glass

YY-_

transition temperature but the observed effect is generally less than for incorporation of (n-octyl-Si) units. Upon pyrolysis of the preceramic polymers containing (n-octyl-Si) units, it appears that the n-octyl group is lost from the ceramic material as an olefin thereby leaving the ceramic material carbon deficient relative to ceramic materials prepared from similar polymers without (n-octyl-Si) units, It is expected that other alkyl groups containing at least six carbon atoms will behave in a similar manner. Phenyl groups are generally not lost upon pyrolysis, Therefore, S pyrolysis of the preceramic polymers containing (phenyl-Si) S units allows more carbon to be incorporated into the final ceramic material and therefore produces ceramic materials that are carbon rich relative to ceramic materials prepared from similar polymers without (phelyl-Si) units, Thus, by incorporation of (RSi) units where R' is n-octyl and phenyl, the relative silicon and carbon ccntent of the resulting ceramic materials can be controlled to a large extent, It is S possible by the practice of t is invention to prepare ceramic materials containing SiC with either excess carbon or excess silicon as well as stoichiometric amounts of silicon and *t'o carbon, Methyl radicals in the form of (CH 3 Si) or ((CH 3 2 Si) units are generally not lost on pyrolysis, Therefore, the relative amounts of silicon and carbon will also depend in Xo° part on the presence of the other units in the polysilane but the incorporation of (n-octyl-Si) and (phenyl-Si) units can be used to "fine tune" the relative silicon and carbon content of the ceramics.

The disilane and monoorganosilane mixtures are reacted in the presence of a rearrangement catalyst, Mixtures containing several disilanes and/or several monoorganosilanes may also be used, Suitable rearrangement catalysts include ammonium halides, tertiary organic amines, -11quaternary ammonium halides, quaternary phosphonium halides, hexamethyiphosphoramide and~ ;,ilver cyanide, Preferred catalyst in~cludes quaternary ammonium halide having the formula W 4 NX', quaternary phosphbnium halides having the formula W4PX', and hexamethylph )sphoramide where W is an alkyl or aryl radical and X' is a halogen, Preferably W is an alkyl radical containing 1 to 65 carbon atoms or a phenyl radical and, X' is chlorine or bromine, one especially preferred catalyst is tetra-'n-buty)phosphonium bromide, The amount of catalyst ut.-ilized can range from *0.001 to 10 weight percent and pref'erably from Q,1 tQ Weight percent based on, the we~ght of the ;starting disilane/monoorcjanosilane mixture, The catalysts and Ot'start~.ng materials require anhydrous conditions and therefore one must take care to insure that moisture is excluded from the reaction system whon the reaci;ants are mixed, Qerally, this can be done by using a stteaffm of dry nitrogen Qo' 4rgon as a blanket over the reaction mi ,ture, The mixture of about 40. tQ 99 Weight percent ,Wdisilane or disilanes and 1 to 60 jpleight percent monoorqano,silaine or mongorganosi lanes are reacted in the presemcq of *O .001 to 10 Weight percent of a, rarrangement cata1l'et at a, Stemperature of 10000 to 340*C Whil~e distilling b~ h volatile materials umntil there is produed the cl containing or bromine-containing polyae of thi t invention. Preferably, the reacitri mixtUr cntdjnB 7Q, ta 99 weight percent dsilane or disilatwps and I -to 30, woigqht percent monoorganosilane or tonoorganosilanes and moot preferably It contains 80 to 9$ Weight percenit disijana or dioilanes and 2 to 20 weight percent orno iln i monoorganosilanes. The order of mixing the reaatantg is not critical, Preferably, the reaction temperature IA5 fr~om, MOO to 30000. When thq final reaction temnperatut-4 is higher th~-h I -12the boiling point of the monoorganosilane, it is preferred that the reaction temperature be raised slowly to the final temperature so that the monoorganosilane will have a greater tenancy to incorporate into the polymer as opposed to simply distilling out of the reaction mixture. The incorporation of the monoorganosilane may also be increased by removing the volatile by-products only in the later stages of the reaction. Typically the reaction is carried out for about 1 to 48 hours although other time durations may be employed.

The polysilanes of this invention may be converted to ceramic materials by pyrol.ysis to an elevated temperature of at least 750 0 C in an inert atmosphere, vacuum or ammoniacontaining atmosphere for a time su:ficient to convert them to a ceramic material, Preferably, the pyrolysis temperature Sis from about 1000 0 C to about 1600 0 C. If the preceramic o polymers are of sufficient viscosity or if they possess a s ciently low melt temperature, they can be shaped and then pyrolyzed to give a ceramic shaped article such as a fiber, Preferably, the preceramic polymer of this invention o has a softening temperature of about 50 C to 300 0 C and most preferably in the range of 70°C to 200 0 C, Such a softening temperature allows for the formation of preceramic fibers by ,o known spinning techniques.

The chlorine- or bromine-containing 1g lysilanes of this invention may also be used to prepare other preceramic 30go/7 ara 83e-l/7 Spolymers as described in Patent Applications\seia o. 'V45.425ft 1, ,zane Preceramic Polymers" and "De a e Alkylpolysilane Preceramic Poljmeswh w ere filed on the same date as So that those skilled in the art can better appreciate and understand the invention, the followhg examples are given. Unless otherwise indicated, all 1) -13percentages are by weight. The examples are intended to illustrate the invention and are not intended to limit the invention.

In the following examples, the analytical methods used were as follows: The glass transition temperature, T was determined on a Thermomechanical Analyzer, Model 1090, from Dupont Instruments. The glass transition temperature is related to the softening point.

Carbon, hydrogen, and nitrogen were determined on a C, H, N Elemental Analyzer, Model 1106, manufactured by Carlo Erba St.rumentazione of Italy. The sample was combusted at 1030 0 C and then passed over a chromium oMide bed at 650 0 C and a copper bed at 650 0 C. The N 2

CO

2 and H 2 0 produced were then separated and detected using a thermal conductivity a a detector.

a Percent silicon was determined by a fusion technique which consisted of converting the silicon material to soluble forms of silicon and then analyzing the soluble material quantitatively for total silicon by atomic absorption spectrometry. Percent chlorine was determined by S fusion of the sample with sodium peroxide and potentiometric S. titration with silver nitrate, Oxygen was determined using a Leco Oxygen Analyzer equipped with an Oxygen Determinater 316 (Model 783700) and an Electrode Furnace EF100 (Model 77600) 4 1 manufactured by Leco Corporation, St. Joseph, Michigan. The oxygen method involves the high temperature carbothermic reduction to CO with CO analysis by IR.

Thermogravimetric analyses (TGA) were carried out on a Netzsch STA 429 (2400 0 C) TGA instrument manufactured by Netzsch Instruments, Selb, West Germany.

The preceramic polymers were fired to elevated temperature using an Astro Industries Furnace 1000A (water _1_1 -14cooled graphite heated model 1000.3060-FP-12), a Lindberg furnace (Heavy Duty SB Type S4877A), or the TGA instrument.

Example 1 This example demonstrates the preparation of a chlorine-containing methylpolysilane with (CGHSi) units.

The source of the disilanes was a Direct Process residue which contained about 9.0 percent ((CHs) .CSi) 2 32.9 percent

(CI)

2 ClSiSiCl 2

CH

3 57.3 percent (CH 3 ClSi) 2 and 0.8 percent low boiling chlorosilanes. In sample A, the disilanes (2120.5 g, 9.7 moles) and 52,5 g (0.25 moles) of phenyltrichlorosilane was reacted in the presence of 20.0 g tetra-n-butylphosphonium chloride by heating the reaction S" mixture from room temperature to 250°C at a rate of 0091 and holding at 250 0 C for 45 minutes while removing volatile by-products by distillation. In sample B, the disilanes (2101,0 g, 9.6 moles) and 157.5 g (0.75 moles) of phenyltrichlorosilane was reacted in the presence of 20.0 g tetra-n-butylphosphonium chloride by heating the reaction mixture from room temperature to 250 0 C at a rate of 2.0 0 C/min and holding at 250°C for 60 minutes while removing volatile by-products by distillation, About 304.1 g and 320.6 g of S the chlorine-containing polysilanes A and B, respectively were obtained. The chlorine-containing polysilane A contained 39.9 percent silicon, 29.5 percent carbon, 6.03 percent hydrogen, and 0.22 percent oxygen. The chlorine content was not determined. The chlorine-containing polysilane B contained 0.45 percent oxygen. The chlorinecontaining polysilane A was converted to a ceramic material in 54.6 percent yield by pyrolysis to 1200 0 C by heating the sample from room temperature to 1200°C at a rate of 5.0 0 C/min and holding at 1200 0 C for two hours under an argon atmosphere. The ceramic material from A contained 70.4 i i percent silicon, 22.4 percent carbon, and 2.2 percent oxygen.

Chlorine was not determined, Example 2 This example demonstrates the p:eparation of a chlorije-containing methylpolysilanes with (CH 3

(CH

2 5 Si) units using the same general procedure as Example 1. The same disilanes (436 g, 2.0 moles) as in Example 1 and n-hexyltrichlorosilane (15.6 g, 0.1 moles) were reacted in the presence of 4.4 g tetra-n-butylphosphonium bromide by heating the reaction mixture from room temperature to 110 0

°C

at a rate of 8.0°C/min, holding at 110°C for 20 minutes, and heating from 110 to 250 0 °C at 2.0 0 C/min while removing volatile by-products by distillation. After the reaction temperature reached 250°C, the heating was discontinued and a torr vacuum was applied for 10 minutes to remove any residual, volatile components. About 60 g of the chlorinecontaining polysilane was obtained. The polysilane was soluble in toluene and had a glass transition temperature of 120,8 0 C. The chlorine-containing polysilane contained 47.1 percent silicon, 25.8 percent carbon, 6.31 percent hydrogen, 17.48 percent chlorine, and 0.86 percent oxygen. The chlorine-containing polysilane was converted to a ceramic material in a 50.0 percent yield by pyrolysis to 1200°C at a rate of 3.0 0 C/min under an argon atmosphere. The ceramic material contained 71.0 percent silicon, 24.3 percent carbon, no detectable hydrogen, 1.0 percent chlorine, and 1.26 percent oxygen.

Example 3 This example demonstrates the preparation of a chlorinse-ontaining methylpolysilanes with (CH,(CH 2 7 Si) units and, (CH,sSi) units using the same general procedure Cs Example 1. The same disilanes (436 g, 2.0 moles) as in Example 1, n-octyltrichlorosilane (5.0 g, 0.2 moles), and phenyltrichlorosilane (21.1 g, 0.1 moles) were reacted in the -16presence of 4.6 g tetra-n-butylphosphonium bromide by heating the reaction mixture from room temperature to 250 0 C at a rate of 1.5 0 C/min while removing volatile by-products by distillation. The resulting chlorine-containing polysilane was dissolved in toluene, filtered, and stripped at 230 0 C and torr for 15 minutes and was obtained in a 60.2 g yield.

The final chlorine-containing polysilane was soluble in toluene and had a glass transition temperature of 111,5 0

C.

The chlorine-containing polysilane contained 42.0 percent silicon, 29.8 percent carbon, 6.13 percent hydrogen, 9.6 percent chlorine, and 1.62 percent oxygen. The chlorinecontaining polysilane was converted to a ceramic material as in Example 2 in a 51.6 percent yield. The ceramic material S contained 64.8 percent silicon, 22.8 percent carbon, S percent hydrogen, 1.0 percent chlorine, and 3.91 percent ,I oxygen.

i r.

Example 4 A chlorine-containing polysilane with (C 6 HsSi) units was prepared by reacting 22.8 g (0.1 moles) o° CH 3 C1 2 SiSiCl1CH 3 and 21.25 g (0.1 moles) phenyltrichlorosilane in the presence of 0,23 g tetra-n-butylphosphonium Sbromide by heating the reaction mixture to 170 0 C at a rate of 1.6°C/min and holding the temperature at 170 0 C for 7 minutes while collecting volatile by-products removed by S distillation. The chlorine-containing polysilane was vacuum stripped at 170 0 C and 1.0 torr for about 15 minutes. About 8.1 g of chlorine-containing polysilane was obtained. The volatile by-products from the reaction and stripping process were combined and analyzed by gas-liquid chromatography (glc). The volatile by-products contained 0.186 moles CH,SiGlI, 0 moles disilane, and 0.033 moles CHSiCI,. Based on these results it appears that about 67 percent of the phenyltrichlorosilane was incorporated into the chlorinecontaining polysilane in the form of (CgHsSi) units. Based

J

-17on the quantities of starting materials and volatile materials found in the distillate, an empirical formula of

(CH

3 Si)(CsHsSi) Cl b where a and b equal 5.1 and respectively, may be calculated. The calculated chlorine content is 33.2 percent.

Example Several chlorine-containing polysilanes containing

(CH

3 Cl i SiCH 2

CH

2 Si) were prepared. Sample A was prepared by reacting 22.8 g (0.1 moles) CH 3 C12SiSiC1 2

CH

3 and 27.6 g (0.1 moles) CH3Cl 2 SiCH 2

CH

2 SiC1 3 in the presence of 0.23 g tetra-n-butylphosphonium bromide by heating the reaction mixture to 280°C at a rate of 1,,2 C/min while collecting volatile by-products removed by distillation. The chlorinecontaining polysilane was vacuum stripped at 220 0 C and torr for about 6 minutes. About 11.41 g of chlorinecontaining polysilane was obtained. The volatile by-products from the reaction and stripping process were combined and analyzed by glc. The volatile by-products contained 0.182 moles CH 3 SiCl,, 0.003 moles disilane, and 0.032 moles

CH

3 Cl 2 SiCH 2

CH

2 SiCl 3 Based on these results it appears that about 68 percent of the CH 3 Cl 2 SiCH 2 CHSiC1 3 was incorporated into the chlorine-containing polysilane in the form of

(CH

3 ClSiCH 2 CH.Si) units. An empirical formula of

(CH

3 Si)(CH 3 C1 2 SiCH 2

CH

2 Si) Cl b where a and b equal 5.4 and 14.5, respectively, may be calculated. The calculated chlorine content is 32.3 percent.

Sample B was prepared in a similar manner by reacting 171 g (0.75 moles) CH 3

CI

2 SiSiCl 2

CH

3 and 138 g moles) CHC1lSiCH 2

CH

2 SiC1 3 in the presence of 1,4 g tetra-n-butylphosphonium bromide by heating the reaction mixture to 310°C at a rate of 1.28 0 C/miin while collecting volatile by-products removed by distillation. The polymer was stripped to remo-re any additional volatiles. About 79.5 g of chlorine-containing polysilane was obtained. The -18volatile were analyzed as above and found to contain 1.50 moles CHSiCl,, e moles disilane, and 0.030 moles

CH

3 C1ISiCH 2 CHSiCl 3 Based on these results it appears that about 94 percent of the CH 3 Cl2SiCH 2

CH

2 SiC1, was incorporated into the chlorine-containing polysilane in the form of

(CH

3 C1 2 SiCH 2 CH.Si) units, An empirical formula of

(CH

3 Si)(CH 3 Cl 2 SiCH 2

CH

2 S) aCl b where a and b equal 129 and 235, respectively, may be calculated. The calculated chlorine content is 39.6 percent.

Example 6 SA chlorine-containing polysilane containing o ((CH 3 2 ClSiCH 2

CH

2 Si) was prepared by reacting 39.9 g (0.175 Smoles) CHCl 2 SiSiClICH 3 and 25.6 g (0.1 moles) (CH3) 2 CISiCH 2

CH

2 SiCl 3 in the presence of 0.40 g tetra-n-butylphosphonium bromide by heating the reaction mixture to 330 0 C at a rate of 5.0 C/min using the same procedures as Example 5. About 15.73 g of chlorinecontaining polysilane was obtained. The volatile by-products S contained 0.30 moles CH 3 SiC1 3 0.004 moles disilane, and 0.012 moles (CH 3 2 ClSiCH 2

CH

2 SiC1 3 Based on these results it appears that about 88 percent of the (CH,) 2 C1SiCH 2

CH

2 SiC1 3 was incorporated into the chlorine-containing polysilane in the form of ((CH 3 2 ClSiCH 2

CH

2 Si) units. An empirical formula of (CH 3 Si)((CH3) 2 ClSiCH2CH 2 Si)aCl b where a and b equal 2.1 and 3.2, respectively, may be calculated. The calculated chlorine content is 28.6 percent.

Example 7 A chlorine-containing polysilane containing (Cl 3 SiCH 2

CH

2 Si) was prepared by reacting 22.8 g (0.1 moles) CHC12SiSiCl 2 CH, and 29.7 g (0.1 moles) Cl 3 SiCHCHSSiCI, in the presence of 0.23 g tetra-n-butylphosphonium bromide by heating the reaction mixture to 300°C at a rate of 4.4 0 C/min using the same procedures as Example 5. About 8.2 g of chlorine-containing polysilane was obtained. The volatile -19by-products contained 0.19 moles CH- 3 SiCl 3 0.00' moles dis~iane, and 0.05 mocles (CH 3 ),ClSiCHCH 2 SiCl.. Based on these results, it appears that about 50 percent of the Cl 3 SiCH 2 C~iI 2 SiCl 3 was incorporated into the chlorinecontaining polysilane in the form of (Cl 3 SiCH 2

CH

2 Si) units.

An empirical formula of (C1 3 SiCH2CH 2 Si) Clwhraanb a bwhraanb equal 1.0 and 2.1, respectively, may be calculated. The calculated chlorine content is 46.9 percent.

Example 8 This example is presented for comparison purposes only. Several attempts were madea to incorporate 2

CHCH

2 Si) units into a chlorine-containing polysilane.

The process of this invention generally resulted in a relatively low percent incorp-ration. In sample A, 22.8 g (0.1 moles) CHC 2 Sai1ij.

2 uri and 19i.2 g (0u.1 moles)

(CH

3 2

CHCH

2 SiCl 3 in the presence of 0.23 g tetra n-utylphosphonium bromide by heating the reaction mixture to 240'C at a rate of 2.4 0 C/min using the samre procedureq as Example Only about 5Q percent of the (CH 3 2 CHCHSiCl 3 was incorporated as 2

CHCH

2 Si) units in thie poly-0-ilane. In sample B, 39.9 g (0.175 moles) CH 3 Cl 2 SiSiCl 2

CH

3 and 19,2 g (0.1 moles) (CH 3 2

CHCH

2 SiC1I in the presenAce of 0.40 g tetra butylpho sphonium bromide by heating the reaction.

mixture to 422'C at a rate of 7,4 0 C/min using the same procedures as Example S. Only about 17 percent of the

(CH

3 2

CHCH

2 SiCl 3 was incorporated as ((CH3) 2

CHCH

2 Si) units in the polysilane. In sample C, 68,4 g (0.3 moles)

CH

3 C1 2 SiSiC1 2 CH, and 38.3 g (0.2 moles) (CH 3 2

CH-CH

2 SiCl 3 in the presence of 0.68 g tetra-n-butyl phosphonium bromide by heating the reaction mixture to 4 00'C, at a rate of 6.2 0 C/min using the same procedures as Example 5, Only about 12 percent of the (CH 3 2

CIICH

2 SiCl 3 was incorporated as ((Cti3) 2

CHCH

2 Si) units in thle polysilane,,

Claims

1. A polysilane, which is solid at 25'C, having the average unit formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl radicals containing 1 to 4 carbon atoms, wherein R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula AX (y)Si(CH 2 Z- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where there are from 0 to mole percent (R 2 Si) units, 1 to 99 mole percent (RSi), and 1 to 99 mole percent (R'Si) units and wherein the remaining bonds on silicon are attached to either other silicon atoms\ chlorine atoms, or bromine atoms. 4m

2. A polysilane as claimed in claim I. wherein there are from 0 to 40 mole percent (R 2 Si) units, 40 to 99 A 4 mole percent (RSi) units, and i to 30 mole percent (R'Si) 0 units. 4 4

3. A polysilane as claimed in claim 1 wherein R* is a radical of the formula Ay X (_ySi(CH 2 Z wherein A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1. -21-

4. A polysilane as claimed in claim 2 wherein the polysilane contains both (n-octyl-Si) units and (phenyl-Si) units.

A method of preparing a polysilane having an average unit formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl radicals containing 1 to 4 carbon atoms, wherein R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A X )Si(CH 2 wherein each A independently selected from Sis a hydrogen atom or alkyl radicals containing 1 to 4 carbon 3,000 atoms, y is an integer equal to 0 to 3, X is chlorine or a; bromine, and z is an integer greatfir than or equal to 1, o wherein there are from 0 to 40 mole percent (R 2 zi) units, 1 to 99 mole percent (RSi) units, and 1 to 99 mole percent (R'Si) units, and where the remaining bonds on silicon are attached to either other silicon atoms, chlorine atoms, or bromine atoms, wherein such method comprises Lt-ating a mixture containing a chlorine-containing or bromine- containing disilane and 1 to 60 weight percent of a mono- organosilane of formula R'SiX 3 where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A X _Si(CH 2 wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, with 0.001 to 10 weight percent of a rearrangement catalyst at a temperature of 100°C to 340°C while distilling by-produced volatile materials until there is produced a polysilane, which is a solid at 25 0 C, having the average 4 -22- formula (R 2 Si)(RSi)(R'Si) wherein each R is independently selected from alkyl radicals containing 1 to 4 carbon atoms, where R' is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A yX(3 _y)Si(CH 2 z wherein each A is independently selected from a hydrogen atom or alkyl radicals containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where there are from 0 to 40 mole ercent (R 2 Si) units, 1 to 99 mole percent (RSi) units, and 1 to 99 Smole percent (R'Si) units and wherein the remaining bonds on silicon are attached to etha other silicon atomsj chlorine Satoms, or bromine atoms.

6, A method as claimed in claim 5 wherein the rearrangement catalyst is selected frQm the group consisting of ammonium halides, tertiary organic amines, quaternary ammonium halides, quaternary phosphonium halides, hexamethyl- phosphoramide, and silver cyanide.

7. A method as claimed in Qlaim 6 wherein the rearrangement catalyst is present at a level of 0.1 to weight percent and is selected from the group consisting of quaternary ammonium halides of general formula W 4 NX', J quaternary phosphonium halides of the general formula WPX*, and hexamethylphosphoramide where W is an alkyl or aryl radical and X' is a halogen. -23-

8. A method as claimed in claim 7 wherein the rearrangement catalyst is tetra-n-butylphosphonium bromide or tetra-n-butylphosphonium chloride, DATED THIS 14TH DAY OF DECEMBER, 1987 DOW CORNING CORPORATION EDWD. WATERS SONS, PATENT ATTORNEYS, QUEEN STREET, MELBOURNE, VICTORIA 3000, AUSTRALIA